This invention relates to an X-ray imaging system which enables taking an X-ray picture of an object at a desired time while fluoroscopic observation is being conducted on the object.
For radiographic examination of the gastro-intestinal tract, it has been customary to administer a dose of contrast medium orally to a person to be examined and observe an area or part of interest of the tract fluoroscopically on a TV monitor, so that the moment the area takes a position and/or assumes a state intended for examination, a high speed exposure is made to a silver halide film, which is developed to produce a picture of the area to be used for diagnosis. In the conventional method of taking X-ray pictures at a high shutter speed by using a silver halide film, it is extremely difficult and requires a great deal of skill to make an exposure exactly at the time a picture useful for diagnosis should be taken since there is a time lag of about 1 (one) second between the time the instructions to take a picture were given and the time an exposure has actually been made. The time lag is chiefly caused by:
(a) the time required for transfer of a film by mechanical means to a position where exposure is to be made, PA0 (b) the time required for the temperature of the filament of the X-ray tube to be raised from the temperature it has when the X-ray flurorscopic view of an object is observed with a relatively low X-ray intensity to the temperature the filament of the X-ray tube has when a picture is to be taken with a higher X-ray intensity, and PA0 (c) the time required for increasing the rotational speed of the target in the X-ray tube, which is rotated to prevent overheating of the focal spot, from a lower speed for fluoroscopic observation of the object to a higher one for photographing thereof.